Altitude sensor



c. M. PERKINS ALTITUDE SENSOR Aug. 4, 1953 Filed Nov. 28, 1950 M mm NM W.n mm m mm on Q. 5

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INVENTOR. CO/PLES M. PER/0N5 Patented Aug. 4, 1953 ALTITUDE SENSORCorles M. Perkins, Rutherford, N. J., assignor to Bendix AviationCorporation, Teterboro, N. J., a corporation of Delaware ApplicationNovember 28, 1950, Serial No. 197,991

The present invention relates to auto pilots eral functions, one ofwhich is to put out a signal which is a measure of rate of climb. Inpresent day aircraft, the range of the rate of climb is from fifty feetper minute to rates in the thousands of feet per minute. This wide rangeof rate of climb presents a problem to find means that will accuratelymeasure the rate of climb through the range. The large dynamic rangerequired is greater than that which can be handled by the conventionalservo means using an aneroid to detect altitude, a linear inductivepick-off to detect movement and position of the aneroid, a motorresponsive to the pick-01f signal to drive me pick-off through a geartrain to the null position and a rate generator to read the speed of themotor indicative of the rate of climb.

A low inertia motor of the type adapted for use in the aforenoted systemcan be controlled to a minimum speed of 100 RP. M. and. the maximumspeed may be as high as 9900 R. P. M. This will provide a dynamic rangeof 90 to l which falls far short of meeting the desired range. Toincrease the maximum speed of the motor would also increase the minimumcontrollable speed of the motor. Loading the motor would lower thecontrollable minimum speed but would not improve the range beyond 200 to1.

Other arrangements have proven unsatisfactory in that they failed toprovide the required range, were unstable or mechanically andelectrically too complicated to be practical.

It is an object of the present invention to overcome the aforenoteddisadvantages and objections by providing an improved system whereby twomotors, essentially identical and each provided with a rate generator,are connected through separate gear trains to drive the linear take-offto null. One of the gear trains has a high reduction and enables themotor attached thereto to take over the control for low rates of climb.Upon the rate exceeding a predetermined maximum, the motor and highreduction gearing are disconnected and the other motor takes over.

Another object of the invention is to provide a two speed altitudesensor.

The above and other objects and features of the invention will appearmore fully hereinafter from a consideration of the following descriptiontaken in connection with the accompanying drawing wherein one embodimentof the inventionis illustrated by way of example,

14 Claims. (Cl. 318-481) In the drawing:

Figure 1 is a diagrammatic showing of an altitude sensing systemembodying the invention.

Figure 2 is a drawing illustrating graphically the operation of theinvention.

Referring now to Figure 1, a pressure responsive device 5 is mountedwith one end fixed and is responsive to pressure change. The other endis connected by a rod 6 to a core 1 of a linear inductive pick-offtransformer 8. The transformer 8 has a primary winding 9 and secondaryWinding II] on pole piece H. The primary winding 9 is connected to asuitable source of alternating current (not shown). The secondarywinding I0 is made up of two sections wound in opposition to each other.The phase and magnitude of the output of the transformer 8 is determinedby the position of the core 1 relative to the winding H]. Th output willbe zero when the core 1 extends an equal distance across the twosections of the winding H1 in the null position.

One end of the winding I0 is connectedto ground and the other end isconnected by conductors l2 and I3 to the inputs of amplifiers l4 and IS.The output of amplifier I4 is connected by conductors l6 and H acrosssignal winding [8 of a motor I 9.

The motor l9 has an excitation winding 20 connected by conductors 2| and22 to a suitable source of alternating current (not shown). Thedirection of rotation of the motor I9 is dependent upon the phase andmagnitude of the current in the signal winding I 8.

A rate generator 23 is attached to armature shaft 24 of the motor l9.The rate generator 23 has an excitation winding 25 connected byconductors 26 and 21 to a suitable alternating current source (notshown) and a signal winding 28. The armature shaft 24 is connected to apinion gear 29 through gears 30, 3|,shaft 32 and gear 33.

In like manner, the output of the amplifier I5 is connected byconductors 34 and 34A to signal winding 35 of a motor 36. The motor 36has an excitation winding 31 connected by conductors 38 and 39 to asuitable alternating current source (not shown). A rate generator 40 isattached to armature shaft 4| of the motor 36. The generator 40 has anexcitation winding 42 connected by conductors 43 and 44 to a suitablesource of alternating current (not shown) and a signal or output winding45.

The armature shaft 4| is connected to the pinion gear 29 through gears46, 41, shaft 48, gears 49, 50, shaft 5|, clutch 52, shaft 53 and gear54. The pinion gear 29 is connected by shaft 55 and gear 55 to rack gear51. The rack gear 51 is connected by a rod 58 to the pole piece ll ofthe transformer 8.

One end of the winding 45 of the generator 40 is connected to ground.The other end of the winding 45 is connected by a conductor 59 to oneend of the winding 28 of the generator 23. The other end of the winding28 is connected to the rate of climb output signal conductor 55.

The clutch 52 connects the shafts and 53 and is actuated by a lever 5|pivoted at 52. The clutch 52 is normally biased in a disengaged positionby spring 53. Connected to the end of the lever 5| is an armature 54 ofa solenoid 55. The solenoid 55 has a control winding 55. Energization ofthe winding 55 is controlled by a centrifugal switch 5? connected to therotor shaft 4| of the motor 35. The switch 51 is illustrated as having afixed contact 58 and a movable contact 59. The movable contact 59 isactuated by ball means I5 responsive to a predetermined speed to actuatethe movable contact 59 to an open circuit position. The stationarycontact is connected by a conductor 1| to one end of the winding 55. Themovable contact 59 is connected by a conductor T2 to one terminal of aD. C. source illustrated as a battery 13. The other terminal of thebattery 13 is connected by a conductor 15 to the other end of thewinding 55. The solenoid 55 when energized, overcomes the bias of thespring 53 and actuates the clutch 52 to an engaged position.

The shaft 55 may also drive an inductive altitude signal developingdevice indicated generally by the numeral I5 or any other control orindicating equipment conventionally used in connection with altitudedisplacement.

In operation, the motors l9 and 35 are substantially identical. The gearreduction from the motor 35 is such that a maximum rate ofsynchronization of, for example, 3500 feet per minute may be obtained.The motor I9 is geared so that a maximum rate of synchronization of tenor more times the rate for motor 35 may be obtained. At low speeds, themotors l9 and 35 are operating on the low torque range of the outputcurves, hence the motor 35 with the larger gear reduction will beeffective in driving the pick-off 8 to null. The motor |9 due to thehigh gear ratio will have insufiicient torque to drive the pinion gear29 faster than it is being driven by the motor 35 and consequently willbe operating at a somewhat lower speed than the motor 35. For theexample given, the motor 35 will have a maximum rate of synchronizationof 60,000 feet per minute and so will be running approximately 17 timesfaster than the motor l9. Thus when the altitude is changing slowly, themotor 35 with the larger reduction gearing will be efi'ective in drivingthe pick-off 8 to null. As the rate of climb increases, the motor 35will gradually approach maximum speed. At a predetermined point justbelow maximum speed, the centrifugal switch 51 will deenergize thesolenoid 55 and the spring 53 will disengage the clutch 52. The motor 35will continue to run at the maximum speed, but will no longer beeffective in driving the pick-off 8 to null. The motor I9, however, willcontinue to drive the pick-off to null, and will be able to carry theunit up to rates of thousands of feet per minute. As the rate of climbdiminishes to within the speed range of the motor 36, the centrifugalswitch 52 will close the contacts 58, 69 causing the solenoid 5 5 4 toactuate the clutch 52 to engage the shaft 5| whereby the motor 35 willagain take over.

The output curve of volts vs. rate of climb will be the sum of theoutput of the rate generators 23 and 40 as the output windings 28 and 45are connected in series. See Figure 2. For rates of climb up to, forexample, 3500 feet per minute the curve will have a relatively steepslope, above that where the rate generator 28 on the motor l9 only isadding to the output, the slope will be smaller. Upon reaching 3500 feetper minute the output of the rate generator 45 will remain constant.Thus, at low rates of climb, the sensitivity is greater than for thehigh rates of climb.

Although only one embodiment of the invention has been illustrated anddescribed, various changes in the form and relative arrangement of theparts, which will now appear to those skilled in the art, may be madewithout departing from the scope of the invention.

I claim:

1. Apparatus for determining the rate of change of altitude of a highspeed aircraft adapted for traversing a wide range of altitude levels,comprising means having a wall movable in one direction in response tocraft ascent and movable in another direction in response to craftdescent, normally balanced means which, when unbalanced, develop asignal correspond ing to the amount of its unbalance, said wall beingadapted to unbalance said normally balanced means, a pair of drivingmeans operative by said signal, common means connecting said drivingmeans to re-balance said normally balanced means when the latter isunbalanced, means driven by one of said driving means for developing asignal corresponding to the rate of operation of the last-named drivingmeans, means responsive to a predetermined rate of wall movement formaking the first driving means inoperative over the re-balancing means,said second driving means assuming primary control of said re-balancingmeans, and means driven by the second driving means for developing arate signal corresponding to the speed of operation of said seconddriving means.

2. Apparatus for determining the amount of altitude change for a highspeed aircraft adapted for traversing a wide range of altitude levels,comprising means having a wall movable in one direction in response tocraft ascent and movable in another direction in response to craftdescent, normally balanced means which, when unbalanced, develop asignal corresponding to the amount of its unbalance, said wall beingadapted to unbalance said normally balanced means, a pair of drivingmeans operative by said signal, common means connecting said drivingmeans to rebalance said normally balanced means when the latter isunbalanced, means adapted to be driven by said common means to give asignal corresponding to the position of said normally balanced means,means responsive to a predetermined rate of wall movement for making oneof said driving means inoperative over the rebalancing means, said otherdriving means assuming control of said rebalancing means, said positionsignal having a high degree of sensitivity when driven by both of saiddriving means and a lesser degree of sensitivity when driven by saidlast named driving means.

3. Apparatus for determining the rate of change of altitude of a highspeed aircraft adapted for traversing a wide range of altitude levels,comprising means having a wall movable in one direction" in response tocraft ascent and mov able inanother directionin response to craftdescent, normally balanced means which, when unbalanced-develop a signalof'phaseand magnitudecorresponding to the rate and direction of unbal'ance, apairof motors operative by'sai'd signal; one of said motorsbeing connected through high reduction gearing to re-balance saidnormally balanced means when the latter is" unbalanced, the other ofsaid motors being connected through low reduction gearing torebalancesaid" normally balanced means when the latter is unbalanced,said first named motor being" adapted to assume primary control of saidrebalancing means below a predetermined rate ofwallmovement, meansresponsive to said predetermined rate for making said first motorinoperative over the rebalancing means, said second motor assumingcontrol of said re-balancing means,- and means-for developing aratesignal corresponding to thespeed of operation of both of' said motors.

4. Apparatus for determining the amount of altitude change'and rate ofaltitude change of a high speedaircraft traversing a wide range ofaltitude levels, comprising means having a wall movable in one directionin response to craft ascent and movable in another direction in responseto craft descent, normally balanced means, which, when unbalanced,develop a signal corresponding to the amount of its unbalance, said wallbeing adapted tounbalance said normally balanced means, a pair ofdriving means operative by said signal, said driving means havingdifferent output ratios, common means connecting said driving means tore-balance said normally balanced means when the latter is unbalanced,meansresponsive to a predetermined rate of wall movement for making oneof said driving means inoperative over the re-balancing means, theother. of said driving means assuming control of said rebalancing means,means driven by said driving means for developing a rate signalcorresponding to the speeds of operation of said driving means, andmeans driven by said common meansfor developing .a. signalcorresponding'to the position of said re-balancing means.

5. Apparatus for determining the rate of change of a high speed aircraftadapted for traversing a wide range of altitude levels, comprising meanshaving a member movable in one direction in response to craft ascent andmovable in another direction in response to craft descent, normallybalanced means which, when unbalanced, develop a signal corresponding tothe amount of its unbalance, said member being adapted to unbalance saidnormally balanced means, driving means responsive to said signal tore-balance said normally balanced means, said driving means includinggearing adapted to balance said re-balancing means at one gear ratio forsignals below a predetermined rate of member movement and at a differentgear ratio for signals above said predetermined rate of member movement,and means driven by said driving means for developing a rate signalcorresponding to the speed of operation of said driving means.

6. An altitude sensor for providing an indication of rate of climbcomprising pressure responsive means, an inductive pick-off responsiveto movement and position of said pressure responsive means, an inductivepick-off responsive to put of said pick-off, a relatively high reductiongear train for connecting said first motor to said pick-off, a secondmotorresponsive tdthe output of" said pick-off, a. relatively. lowreduction gear train" for connecting said: second mo-i torto saidpick-off, said; motors havinglow torque at low speedsysaid first motor.and high reduction gear train being adapted? to drive said pick-ofi toanull position for. low rates of climb; means-'i'or disconnecting saidhigh reduction gear train from said pick oii upon: said first: motorreaching a predetermined maximum speed, said secondmotor being adapted.tozdrive; saidpick-ofi to anull'position for rates of :climbabovesaidpredetermined maximum, and' means for derivinga signal corresponding tothe speeds of. said: mo: tors.

'T. A rateof climb sensing device comprisingan altitude pressureresponsive device, an; inductive pick-off transformer responsive tomovementand positionof said pressure device, apairrof motors responsiveto the output of; said transformer to drive said transformer to anullposition, oneof said motors having a. relatively high reductiongearing and-adaptedto be effective in driving said transformer to null.position for low ratesof climb, centrifugal means for disconnectingvsaidmotor and high reduction gearing from driving said transformer uponsaid motor reaching a; predetermined maXimum-speed, said othermotorybecoming-effective for drivingsaid-transformer to-a null positionfor high. rates. of climb. and means for deriving a rate signal'fromboth of. said motors.

8. A two speed altitude sensor. comprising-a pressure responsive devicefor detecting. altitude, inductive means for producing'a signal ofmagnitude and phase dependent upon movement and position of saidpressure-responsive device, dual driving means responsive'to theoutput-signal of said inductive means 'for driving. said inductive meansto a null position, one of said driving means being adapted to drivesaid inductive means for low rates of climb, the other of said drivingmeans being adapted to drive saidinductive means at high rates of'climb,means responsive-to a predetermined rate of climb to disconnect saidfirst named driving means from said inductive means, and means.responsive to the combined rates of said driving means to derive asignal proportional to the speed of said driving means.

9. Apparatus for deriving a signal indicative of the rate of change ofaltitude of a high speed aircraft traversing a wide range of altitudelevels, comprising means having a wall movable in one direction inresponse to craft ascent and in another direction in response to craftdescent, means operative by the wall for developing a control signalcorresponding to wall movement, motor driven means responsive to saidcontrol signal for developing a signal indicative of the rate of changeof altitude, said signal having a relatively steep slope for low ratesof wall movement and a lesser slope for high rates of Wall movement.

10. Apparatus for determining the rate of change of altitude andaltitude of a high speed aircraft adapted for traversing a. wide rangeof altitude levels, comprising means having a wall movable in onedirection in response to craft ascent and movable in another directionin response to craft descent, normally balanced means which, whenunbalanced, develop a signal corresponding to the amount of itsunbalance, said wall being adapted to unbalance said normally balancedmeans, a pair of driving means operative by said signal, common meansconnecting said driving means to re-balance said normally balanced meanswhen the latter is unbalanced, means also driven by said common meansfor developing a signal corresponding to the operation of said commonmeans to indicate the change of altitude, means driven by one of saiddriving means for developing a signal corresponding to the rate ofoperation of the last-named driving means, and. means responsive to apredetermined rate of wall movement for making the first driving meansinoperative over the re-balancing means, said second driving meansassuming primary control of said re-balancing means, and means driven bythe second driving means for developing a rate signal corresponding tothe speed of operation of said second driving means.

11. Apparatus for determining the change of altitude of a high speedaircraft adapted for traversing a wide range of altitude levels,comprising means having a wall movable in one direction in response tocraft ascent and movable in another direction in response to craftdescent, normally balanced means which, when unbalanced, develop asignal corresponding to the amount of its unbalance, said wall beingadapted to unbalance said normally balanced means, a pair of drivingmeans operative by said signal, common means connecting said drivingmeans to re-balance said normally balanced means when the latter isunbalanced, means also driven by said common means for developing asignal corresponding to the operation of said common means to indicatethe change of altitude, and means responsive to a predetermined rate ofwall movement for making the first driving means inoperative over there-balancing means, said second driving means assuming primary controlof said re-balancing means.

12. Apparatus for developing a signal indicative of a rate of change incondition, comprising a two part device having a first part movable froma null position relative to a second part in response to change incondition for developing a signal, means responsive to said signal fordriving the second part relative to the first part to re-establish saidnull position, said driving means including a plurality of means fordriving said second part to the null position at difierent rates, meansresponsive to said driving rate for rendering selective drivesineffective, and mean operated by said driving means for developing asignal whereby the latter signal is the rate of change of null positionand indicative of a rate of change of condition.

13. In a null seeking system, a plurality of motors, means displaceablefrom a predetermined position to provide a source of control energy forsaid motors, means connecting said motors and said displaceable meansfor returning said displaceable means to said predetermined position forcancelling said control energy, said connecting means including meansfor returning said displaceable means to a predetermined position at afast rate and means for returning said displaceable means to saidpredetermined position at a slow rate and means responsive to the rateof returning said displaceable means to said predetermined position forselectively rendering one of said returning means ineffective.

14. A variable speed sensor for control conditions comprising a deviceresponsive by movement for detecting a change in control condition,signal means associated with said detecting device for producing asignal of a phase and a magnitude dependent upon the direction andextent of movement of said detecting device, plural driving meansresponsive to the output signal of said signal means for driving saidsignal means to a null position, one of said driving means being adaptedto drive said signal means for low rates of movement, the other of saiddriving means being adapted to drive said signal means at high rates ofmovement, means responsive to a predetermined rate of movement todisconnect said first named driving means from said signal means, andmeans responsive to the combined rates of said driving means to derive asignal proportional to the speeds of said driving means.

CORLES M. PERKINS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,768,966 Tanner July 1, 1930 1,997,412 Fischel Apr. 9, 19352,105,598 Hubbard Jan. 18, 1938 2,419,812 Bedford Apr. 29, 19472,486,935 Fanta, Jr. Nov. 1, 1949

